Sex only burns about 21 calories, according to new university study

Burning love apparently does not equate to burning fat. A new study from the University of Alabama at Birmingham says the average sex act burns only about 21 calories.

The study, published Wednesday in the New England Journal of Medicine, contradicts many long-standing claims that sexual activity is a vigorous, fat-burning workout. Funded in part by the National Institutes of Health, the study results found that “false and scientifically unsupported beliefs about obesity are pervasive in both scientific literature and the popular press.”

Most online claims about the calorie burning potential of sexual activity are based on one-hour increments, whereas this study worked off an average time span of six minutes per sexual encounter.

The study’s director, Dr. David Allison, who also serves as director of the university's Nutrition Obesity Research Center, tested a number of theories in his study, including whether physical education classes actually improved a child’s health and whether skipping breakfast or snacking contributed to weight gain.

“As health professionals, we should hold ourselves to high standards so that public health statements are based on rigorous science," Allison said in a statement. “The evidence is what matters.

However, CBS News notes that some fellow experts question the motivations behind the study, noting that some of the participants received funding from sources including Coca-Cola, the McDonald’s Global Advisory Council and two obesity drug manufacturers—Vivus and Arena Pharmaceuticals.

Allison responds that his team’s research was motivated by a desire to counter health theories propagated as fact by self-proclaimed health experts.

"From social media outlets like Facebook, to mainstream television news to dietetics and nutrition textbooks, these myths are perpetuated, irrespective of the scientific evidence," study co-author Dr. Krista Casazza told CBS News. "As scientists, we have the responsibility to present the evidence as it exists without inflating ideas and contributing to popular misconceptions. As a registered dietitian, I feel that providing evidence-based statements about weight loss is essential."